Unity gain amplifiers are used in variety of applications. In one application, a unity gain amplifier is used to convert an external power supply voltage to an internal power supply voltage source for an integrated circuit. Often the external power supply voltage has noise that is undesirable. In addition, the external power supply may not be at the correct voltage for the internal circuitry. A unity gain amplifier is used to provide the correct internal voltage. One problem with some previous solutions is that the amplifier exhibits ringing and instability due to overshoot. As a result, any noise on the external power supply and the reference voltage are transferred to the internal power supply. Another previous solution has better noise immunity, but requires a very large compensation capacitor. The large compensation capacitor takes up valuable die space. Both of the previous solutions can be exacerbated by low power, low voltage constraints.
Thus there exists a need for a unity gain amplifier that does not exhibit stability problems and does not require a huge compensation capacitor.